/Engine/Plugins/Online/OnlineSubsystem/Source/Public/Interfaces/OnlineSessionInterface.h
virtual [FDelegateHandle](API\Runtime\Core\Delegates\FDelegateHandle) AddOnSessionParticipantJoinedDelegate_Handle ( const [FOnSessionParticipantJoinedDelegate](API\Plugins\OnlineSubsystem\Interfaces\FOnSessionParticipantJoinedDeleg-) & Delegate )